Organic light emitting devices (OLEDs) are devices, in which the electroluminescent layer is a film containing at least one organic compound that emits light in response to an electric current. Most OLEDs consist of a stack of different aromatic compounds with well-defined HOMO and LUMO levels. Such compounds are generally classified as electroluminescent materials and charge transport materials. Several properties required for such electroluminescent and charge transport compounds include high fluorescent quantum yield in solid state, high mobility of electrons and holes, chemical stability during vapor-deposition in vacuum, and the ability to form stable films. Common problems with OLEDs include fast aging/short life span, undesirably high operating voltages, or insufficient efficiency. Thus, here is a need for new compounds for OLED devices that enable long-lasting and highly efficient devices. Compounds with these characteristics typically require specific HOMO and LUMO energy levels, and a sufficient energy gap between HOMO and LUMO. Furthermore, compounds with high triplet energies are particularly desirable to support phosphorescent emitters.
KR2009131958A (Abstract) discloses a diverse set of aromatic compounds, including a specific 2-(quinoline-6-yl)-benzoxazole example for use in organic photoelectric devices. Such compounds are disclosed as having an inherent dipole moment, which leads to an improvement in charge mobility and various optical properties, and are disclosed as having lifetime, efficiency, thermal and electrochemical stability.
Other quinoline-benzoxazole compounds are disclosed in the following references. EP1460067A1; JP2011168515A (Abstract); JP2000017261A (Abstract); JP2000191657 (Abstract); US20110081428; WO2009021750; WO2008073451; WO2002016333; WO1996009822; EP694599A2; EP641850A1; EP640676A1; EP640677A1; and WO1992015579. However, as discussed above, there remains a need for new compounds for OLED devices that enable long-lasting and highly efficient devices, and which are suitable for use both with fluorescent and phosphorescent emitters. These needs and others have been met by the following invention.